1. Field of the Invention
The present invention generally relates to a method of producing high dielectric constant materials on a semiconductor substrate and, more particularly, to a method of improving the quality of tantalum pentoxide (Ta.sub.2 O.sub.5) films with low temperature annealing.
2. Description of the Prior Art
High dielectric constant (dc) materials are useful as capacitor dielectrics of the storage capacitor in dynamic random access memories (DRAMs). High dc Ta.sub.2 O.sub.5 film has been seriously studied as a storage capacitor dielectric for 64 and 256 Mbit dynamic random access memories (DRAMs), especially for stack capacitor structures. Most of these films are deposited at low temperature (i.e., 400.degree.-480.degree. C.) using chemical vapor deposition (CVD). However, the primary disadvantage of Ta.sub.2 O.sub.5 as compared to insulators with lower dielectric constants is its fairly high conductivity with substantial current leakage due to either deviation from stoichiometric composition or defective bonding. Therefore, Ta.sub.2 O.sub.5 films require substantially a higher temperature (i.e., 750.degree.-800.degree. C.) annealing cycle to improve the film's electrical properties. One method is Rapid Thermal Oxidation (RTO). The high temperatures used in this method may cause oxidation of nearby polysilicon, degrading the dielectric properties. Another method used is ultraviolet (UV) ozone in which samples are exposed to UV light under ozone ambient. UV ozone has a long processing time and may also cause high temperatures locally. Ozone plasma has been studied as a "low temperature plasma oxidation process" to grow excellent thin silicon oxide film. However, the use of plasma oxidation to improve other high dielectric constant materials has not been done.